The present invention relates to a coupler plug that includes a housing, namely a basic body and a cover element, a sensor unit having electrical contact elements, in particular for a planar broadband Lambda sensor, and an adjustment element that is connected to the sensor unit.
Generally, coupler plugs of the aforementioned type are designed as Lambda sensors, the connectors that are provided in the coupler plug being provided for adjustment, signals, and heating the sensor. Conventionally, the Lambda sensor and the Lambda regulator, in conjunction with a three-way catalytic converter, constitute an effective method for cleaning exhaust gas. The Lambda sensor, which is for example screwed into an exhaust gas system, includes a measuring sensor for determining the oxygen content in the exhaust gas. The residual oxygen content is very suitable for use as a measured quantity and regulates the air-fuel ratio, as it indicates precisely whether the air-fuel mixture is combusting completely.
Herein, the Lambda sensor sends a voltage signal, which represents the current value for the composition of the mixture and tracks changes in the mixture. The fuel supplied to the engine is regulated by a mixture preparation system as a function of the Lambda sensor signal, so that a stoichiometric air-fuel ratio of xcex=1 is achieved. Depending on the design of the exhaust gas system and the application, heated or non-heated sensors are used. Lambda sensors can also be used in applications other than fuel-powered vehicles, e.g., in order to regulate gas-powered engines or oil/gas burners.
Broadband Lambda sensors are modular in design, and in conjunction with planar technology allow a plurality of functions to be integrated. As a rule, they have function layers that include a porous protective layer, an outer electrode, a sensor foil, an inner electrode, a reference air channel foil, an insulating layer, a heater, a heating foil, and connector contacts.
As the broadband Lambda sensor includes a combination of a Nernst concentration cell (=sensor cell) and a pump cell that transports oxygen ions, it can take very precise measurements, not only at the stoichiometric point where xcex=1 but also in the lean and rich ranges.
Each sensor must be individually adjusted. To accomplish this, the sensor has an installed resistor (mini-hybrid). Adjustment, which is preferably carried out using a laser beam, is carried out by removing as necessary the resistor layer that is provided on a ceramic substrate, this resulting in a change in the resistance, adjustment thus being accomplished.
Until now, adjustment has been carried out by bringing the housing of the coupler plug in which the resistor is installed to the adjustment location without the cover element. The cover element is put on after adjustment, via laser processing, has been performed.
To keep moisture, dirt, or similar from penetrating the coupler plug, the cover element has additional seals.
One disadvantage of the conventional embodiment of the coupler plug described above is that additional operation steps and assembly steps are required to close off the coupler plug in the functionally correct manner following adjustment.
Furthermore, an additional cover element along with a seal has to be manufactured and made available in the area where adjustment is performed.
One object of the present invention is to create a further refinement of an embodiment of the coupler plug that is suitable in particular for applications where a planar broadband Lambda sensor is used, so that the coupler plug can be manufactured very inexpensively and has very small dimensions.
This object is achieved by designing part of the coupler plug as a contact carrier, electrical contacts of the coupler plug and the adjustment element being pre-mounted on the contact carrier, and it being possible to separate the contact carrier, along with the electrical contacts and the adjustment element, from the rest of the coupler plug.
An advantage of the present invention is that the coupler plug can be manufactured very inexpensively due to the compactness of the parts to be produced. As a result, the entire coupler plug can be pushed into a grooved tube due to its small size and small outer dimensions.
Moreover, in an example embodiment of the present invention, the same components, in particular for the plurality of electrical contact elements that are to be provided in the housing of the coupler plug, are used. This simplifies the assembly process.
It is advantageous that part of the coupler plug may be designed as a contact carrier, electrical contacts of the coupler plug and the adjustment element being pre-mounted on the contact carrier, and it being possible to separate the contact carrier, along with the electrical contacts and the adjustment element, from the rest of the coupler plug. Alternatively, the electrical contacts only are already arranged in the contact carrier. This can be accomplished, for example, by mounting them by pressing them in or by injecting plastic around them.
For assembly, it may be advantageous that the contact carrier, as a pre-assembled component, can be joined to the rest of the coupler plug without additional tools. Guide elements may be provided to ensure the contact carrier is positioned correctly, and stop-lock means are provided to fix it in place.
A further component, e.g., a secondary interlock element, may be arranged between the contact carrier and the rest of the coupler plug. This constitutes a connecting element between the contact carrier and the rest of the coupler plug, and also ensures that the electrical contacts are positioned correctly in terms of their position and function.
As the basic carrier is completely surrounded by the cover element, the interior of the sensor unit can be sealed off via an arrangement of sealing lips inside the cover element or an arrangement of seals on the basic carrier, so that the interior is protected against sprayed water and/or dirt, for example.
In addition, this helps lock the basic body to the cover element. Initial locking and final locking, i.e., primary interlocking and secondary interlocking, may be provided. The secondary interlock element performs the function of secondary interlocking.
Primary interlocking is carried out in two stages. In a first stage, the cover element is locked so that it is held on the basic body. Then, when the cover element is subjected to further pressure in the direction of the basic body, the secondary interlock element, which has been inserted into the basic body, is fixed in position against the electrical contact element that is guided in the basic body, e.g., a flat female terminal, and is connected to the Lambda sensor. However, this fixing in position is carried out only so that the secondary interlock element is pressed against the contact element, so that a firm connection is created between the contact element and the secondary interlock element. The secondary interlock element is held in the basic body subject to a positive lock, i.e., when the contact element is in the fixed state, the secondary interlock element can only move in the axial direction of mounting of the cover. Support elements that point away from the secondary interlock element are also provided on the secondary interlock element, these extending in the direction of the cover element.
When the secondary interlock element is in the non-operated state, i.e., the contact element has not been fixed in position, the support elements extend well beyond the coupler plug""s basic body, so that the cover element can only complete the first locking stage of primary interlocking. Thus, the cover element can only complete the second locking stage of primary interlocking if complete operation has been performed and the contact element has been correctly fixed in position. This has the advantage that a check can easily be performed as to whether a good contact has been created successfully and the electrical contact element is also reliably secured to the Lambda sensor, and whether the cover element has closed off the basic body with a tight seal.
It may be advantageous if the securing devices are provided at the edge of the cover element, thus allowing the coupler plug to be attached to a further component, e.g., via a groove-tongue connection; or alternatively securing devices are designed so that electrical lines can be attached to the coupler plug.
An arrangement for attaching spray water grommets can be provided as an optional feature.
Another advantage of the present invention is that the aforementioned seals can be injection-molded onto the cover element so that they cannot be lost.
To ensure the transition resistance between the sensor unit and the electrical contact elements remains constant, a soldered join may be provided.
In the example embodiment, it is advantageous that the cover element is made of PBT (polybutylene terephthalate) or equivalent materials.